1. Technical Field
The present invention relates to a method of manufacturing a porous insulating film, a method of manufacturing a semiconductor device, and a semiconductor device.
2. Related Art
In recent years, as line width reduction of interconnect progresses, there has been a problem caused by an increase in the interconnect capacity. In order to suppress the increase in the interconnect capacity, it is effective to lower the dielectric constant of the insulating film in which interconnects are buried. As a method of lowering the dielectric constant of an insulating film, there may be mentioned a method of using an insulating material having a lower relative permittivity than that of silicon oxide, in the insulating film.
More recently, the development of a porous insulating film having fine pores introduced into the insulating film is in progress, in order to further lower the dielectric constant of the insulating film. The porous insulating film is formed by separately introducing a precursor of the insulating film and a porogen into a vacuum vessel, forming an insulating film containing the porogen, and removing the porogen from the insulating film by a heat treatment or the like (see, for example, Japanese Unexamined patent publication NO. 2004-274052, Japanese translation of PCT international application NO. 2005-524983, and Japanese Unexamined patent publication NO. 2007-204850).
WO 2005/053009 describes a technique of forming a porous insulating film using an organic silica compound having a cyclic silica skeleton. It is described in this technique that the cyclic silica skeleton corresponds to the pores.
In the case of forming an insulating film containing a porogen by separately introducing a precursor of the insulating film and the porogen into a vacuum vessel, the porogen aggregates upon being incorporated into the insulating film, and thereby the size of the pores in the porous insulating film undergoes enlargement. Furthermore, in the technique described in WO 2005/053009, sufficient strength of the porous insulating film could not be secured.